Systems and methods for implanting a medical electrical lead

ABSTRACT

Implant tools and techniques for implantation of a medical lead, catheter or other implantable component are provided. The implant tools and techniques are particularly useful in implanting medical electrical leads in implant locations such as substernal spaces or subcutaneous locations. The implant tools include a sheath coupled to a sealing device. The sheath includes a continuous lumen that is in fluid communication with a passage of the sealing device. The lead is advanced through the passage and the lumen for placement of the distal end of the lead at the implant location.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalApplication No. 61/820,014, filed on May 6, 2013, the content of whichis incorporated herein by reference in its entirety.

FIELD

The disclosure relates generally to implantable medical devices of thetype for performing monitoring of a physiologic state and/or therapydelivery. In particular, the disclosure pertains to tools for implantingmedical electrical leads for the physiologic state monitoring and/ortherapy delivery.

BACKGROUND

Implantable cardiac defibrillator (ICD) systems are used to deliver highenergy electrical pulses or shocks to a patient's heart to terminatelife threatening arrhythmias, such ventricular fibrillation. TraditionalICD systems include a housing that encloses a pulse generator and otherelectronics of the ICD and is implanted subcutaneously in the chest ofthe patient. The housing is connected to one or more implantable medicalelectrical leads that are implanted within the heart.

Traditional ICD systems that utilize transvenous leads may not be thepreferable ICD system for all patients. For example, in some patients,difficult vascular access precludes placement of transvenous leads. Asanother example, children and other younger patients may also becandidates for non-transvenous ICD systems. Moreover, transvenous leadsmay become fibrosed in the heart over time, making lead revision andextraction procedures challenging.

A subcutaneous ICD system may be preferred for some patients. Asubcutaneous ICD system includes a lead (or leads) that are implantedsubcutaneously in the patient, i.e., between the skin and the ribsand/or sternum of the patient. As such, the subcutaneous ICD mayeliminate the need for transvenous leads being within the heart. A needexists for tools and methods for delivery of non-transvenous leads toimplant locations other than to the heart.

SUMMARY

This disclosure, among other things, describes techniques, devices andmethods for implantation of an implantable medical lead. Exemplaryimplantation devices comprise a sheath having a proximal end and adistal end with a lumen extending between the proximal end and thedistal end, a sealing assembly coupled to the sheath, the sealingassembly having a passage therethrough that is in substantial axialalignment with the lumen, and an elongate tool configured to be disposedwithin the passage and the inner lumen and having a pre-biased curvatureformed along a length of a body of the elongate tool, wherein thepre-biased curvature orients a distal portion of the elongate tool alonga first plane that is different from a plane defined by a proximalportion of the elongate tool.

Other aspects of the disclosure include methods for implanting animplantable medical lead comprising providing a delivery systemcomprising a sheath having a lumen and a sealing assembly having apassage that is in fluid communication with the lumen, and an elongatetool disposed within the lumen and the passage, inserting the deliverysystem through an access point into the substernal space, orienting adistal portion of the delivery system towards a sternum of the patient,advancing the delivery system through the substernal space to apredetermined implant site, removing the elongate body from the lumenand the passage and inserting a lead through the passage into the lumen,and advancing the lead of the implantable medical system to position adistal end of the lead at the predetermined location.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary embodiments of the compositions and methods accordingto the invention will be described in detail, with reference to thefollowing figures wherein:

FIG. 1A is a front view of a patient implanted with implantable cardiacsystem;

FIG. 1B is a side view the patient implanted with implantable cardiacsystem;

FIG. 1C is a transverse view of the patient implanted with implantablecardiac system;

FIG. 2 depicts a perspective view of an embodiment of a delivery systemfor implanting a medical electrical lead;

FIG. 3A depicts a side cross-sectional view of an embodiment of adelivery system for implanting a medical electrical lead;

FIG. 3B shows a transverse sectional view of an embodiment of a deliverysystem for implanting a medical electrical lead;

FIG. 4 depicts a perspective view of an alternative embodiment of adelivery system for implanting a medical electrical lead;

FIG. 5 depicts a perspective view of an alternative embodiment of adelivery system for implanting a medical electrical lead;

FIG. 6 depicts a perspective view of an alternative embodiment of adelivery system for implanting a medical electrical lead;

FIG. 7 illustrates a side cross-sectional view of an alternativeembodiment of a portion of a delivery system;

FIG. 8 illustrates a side cross-sectional view of an alternativeembodiment of a portion of a delivery system;

FIG. 9 illustrates a side cross-sectional view of an alternativeembodiment of a portion of a delivery system;

FIG. 10 illustrates a transverse cross-sectional view of an alternativeembodiment of a portion of a delivery system;

FIG. 11 illustrates a transverse cross-sectional view of an alternativeembodiment of a portion of a delivery system;

FIG. 12 illustrates a transverse cross-sectional view of an alternativeembodiment of a portion of a delivery system;

FIG. 13 depicts an alternative embodiment of a delivery system forimplanting a medical electrical lead;

FIG. 14 depicts a partial side cross-sectional view of a portion of thedelivery systems in accordance with some embodiments;

FIG. 15A shows a transverse sectional view of a portion of the deliverysystems in accordance with some embodiments;

FIG. 15B shows a transverse sectional view of a portion of the deliverysystems in accordance with some embodiments;

FIG. 16 is a flow chart depicting a method of implanting a leadaccording to an embodiment of the disclosure;

FIGS. 17-19 are partial perspective views that illustrate the method ofimplanting a lead of FIG. 16.

The following detailed description is to be read with reference to thefigures, in which like elements in different figures have like referencenumerals. The figures, which are not necessarily to scale, depictselected embodiments and are not intended to limit the scope of thepresent teachings. Skilled artisans will recognize the examples providedherein have many useful alternatives and fall within the scope of thepresent teachings.

DETAILED DESCRIPTION

In this disclosure, techniques, components, assemblies, and methods fordelivery of a lead into a targeted delivery site within a substernalspace are described. The lead may be delivered through a surgicalincision created on the skin/tissue adjacent to or below the xiphoidprocess (also referred to as “subxiphoid”) to form an access point tothe substernal space, and advancing the lead with the aid of a deliverysystem through which the lead is inserted into the substernal space. Theaccess point may also be formed at the notch (not shown) that connectsthe xiphoid process to the sternum. In other embodiments, the substernalspace may also be accessed through the manubrium.

In this disclosure, “substernal space” refers to the region defined bythe undersurface between the sternum and the body cavity but notincluding the pericardium. In other words, the region is posterior tothe sternum and anterior to the ascending aorta. The substernal spacemay alternatively be referred to by the terms “retrosternal space” or“mediastinum” or “infrasternal” as is known to those skilled in the artand includes the region referred to as the anterior mediastinum. Thesubsternal space may also include the anatomical region described inBaudoin, Y. P., et al., entitled “The superior epigastric artery doesnot pass through Larrey's space (trigonum sternocostale).” Surg. Radiol.Anat. 25.3-4 (2003): 259-62 as Larrey's space. For ease of description,the term substernal space will be used in this disclosure, it beingunderstood that the term is interchangeable with any of the otheraforementioned terms.

In this disclosure, the term “extra-pericardial” space refers to regionaround the outer heart surface, but not within the pericardialsac/space. The region defined as the extra-pericardial space includesthe gap, tissue, bone, or other anatomical features around the perimeterof, and adjacent to the pericardium.

FIGS. 1A-C are conceptual diagrams of a patient 12 implanted with anexample implantable cardiac system 10. FIG. 1A is a front view ofpatient 12 implanted with implantable cardiac system 10. FIG. 1B is aside view patient 12 with implantable cardiac system 10. FIG. 1C is atransverse view of patient 12 with implantable cardiac system 10.

Implantable cardiac system 10 includes an implantable cardiacdefibrillator (ICD) 14 connected to a first lead 16 and a second lead18. The first lead 16 and the second lead 18 may be utilized to providean electrical stimulation therapy such as pacing or defibrillation. Forexample, lead 16 may provide defibrillation therapy while lead 18 mayprovide pacing therapy, or vice versa, while in other embodiments, bothlead 16 and lead 18 may provide pacing therapy or defibrillationtherapy. In the example illustrated in FIGS. 1A-C ICD 14 is implantedsubcutaneously on the left midaxillary of patient 12. ICD 14 may,however, be implanted at other subcutaneous locations on patient 12 asdescribed later.

Lead 16 includes a proximal end that is connected to ICD 14 and a distalend that includes one or more electrodes. Lead 16 extends subcutaneouslyfrom ICD 14 toward xiphoid process 20. At a location near xiphoidprocess 20, lead 16 bends or turns and extends subcutaneously superior,substantially parallel to sternum 22. The distal end of lead 16 may bepositioned near the second or third rib. However, the distal end of lead16 may be positioned further superior or inferior depending on thelocation of ICD 14 and other factors. Although illustrated as beingoffset laterally from and extending substantially parallel to sternum 22in the example of FIGS. 1A-C, lead 16 may be implanted over sternum 22,offset from sternum 22, but not parallel to sternum 22 (e.g., angledlateral from sternum 22 at either the proximal or distal end).

Lead 16 includes a defibrillation electrode 24, which may include anelongated coil electrode or a ribbon electrode, toward the distal end oflead 16. Lead 16 is placed such that a therapy vector betweendefibrillation electrode 24 and a housing or can electrode of ICD 14 issubstantially across the ventricle of heart 26.

Lead 16 may also include one or more sensing electrodes, such as sensingelectrodes 28 and 30, located toward the distal end of lead 16. In theexample illustrated in FIGS. 1A-C, sensing electrode 28 and 30 areseparated from one another by defibrillation electrode 24. ICD 14 maysense electrical activity of heart 26 via a combination of sensingvectors that include combinations of electrodes 28 and 30 and thehousing or can electrode of ICD 14. For example, ICD 14 may obtainelectrical signals sensed using a sensing vector between electrodes 28and 30, obtain electrical signals sensed using a sensing vector betweenelectrode 28 and the conductive housing or can electrode of ICD 14,obtain electrical signals sensed using a sensing vector betweenelectrode 30 and the conductive housing or can electrode of ICD 14, or acombination thereof. In some instances, ICD 14 may even sense cardiacelectrical signals using a sensing vector that includes defibrillationelectrode 24.

Lead 18 includes a proximal end that is connected to ICD 14 and a distalend that includes one or more electrodes. Lead 18 extends subcutaneouslyfrom ICD 14 toward xiphoid process 20. At a location near xiphoidprocess 20, the lead 18 bends or turns and extends superior upward inthe substernal space. In one example, lead 18 may be placed in themediastinum 36 and, more particularly, in the anterior mediastinum. Theanterior mediastinum is bounded laterally by pleurae 40, posteriorly bypericardium 38, and anteriorly by sternum 22. Lead 18 may be implantedwithin the mediastinum such that one or more electrodes 32 and 34 arelocated over a cardiac silhouette of the ventricle as observed viafluoroscopy. In the example illustrated in FIGS. 1A-C, lead 18 islocated substantially centered under sternum 22. In other instances,however, lead 18 may be implanted such that it is offset laterally fromthe center of sternum 22. Although described herein as being implantedin the substernal space, the mediastinum, or the anterior mediastinum,lead 18 may be implanted in other extra-pericardial locations.

Lead 18 includes electrodes 32 and 34 located near a distal end of lead18. Electrodes 32 and 34 may comprise ring electrodes, hemisphericalelectrodes, coil electrodes, helical electrodes, ribbon electrodes, orother types of electrodes, or combinations thereof. Electrodes 32 and 34may be the same type of electrodes or different types of electrodes. Inthe example illustrated in FIGS. 1A-C electrode 32 is a hemisphericalelectrode and electrode 34 is a ring or coil electrode.

ICD 14 may deliver pacing pulses to heart 26 via a pacing or therapyvector that includes any combination of one or both of electrodes 32 and34 and a housing electrode or can electrode of ICD 14. For example, ICD14 may deliver pacing pulses using a pacing or therapy vector betweenelectrodes 32 and 34, deliver pacing pulses using a pacing or therapyvector between electrodes 32 and the conductive housing or can electrodeof ICD 14, deliver pacing pulses using a pacing or therapy vectorbetween electrodes 34 and the conductive housing or can electrode of ICD14, or a combination thereof. In some instances, ICD 14 may deliverpacing therapy via a therapy vector between one of electrode 32 (orelectrode 34) and defibrillation electrode 24. In still furtherinstances, ICD 14 may deliver pacing therapy via a therapy vectorbetween one of electrode 32 (or electrode 34) and one of sensingelectrodes 28 or 30. ICD 14 may generate and deliver the pacing pulsesto provide anti-tachycardia pacing (ATP), bradycardia pacing, post shockpacing, or other pacing therapies or combination of pacing therapies. Inthis manner, ATP therapy or post shock pacing (or other pacing therapy)may be provided in an ICD system without entering the vasculature or thepericardial space, nor making intimate contact with the heart.

ICD 14 may generate and deliver pacing pulses with any of a number ofamplitudes and pulse widths to capture heart 26. The pacing thresholdsof heart 26 when delivering pacing pulses substernally using lead 18 maydepend upon a number of factors, including location of electrodes 32 and34, location of ICD 14, physical abnormalities of heart 26 (e.g.,pericardial adhesions), or other factors. The pacing thresholds neededto capture heart 26 tend to increase with shorter pulse widths. In thecase of ATP, ICD 14 may deliver pacing pulses having longer pulse widthsthan conventional ATP pulses to reduce the amplitude of the pacingpulses. For example, ICD 14 may be configured to deliver pacing pulseshaving pulse widths or durations of greater than or equal to one (1)millisecond. In another example, ICD 14 may be configured to deliverpacing pulses having pulse widths or durations of greater than or equalto ten (10) milliseconds. In a further example, ICD 14 may be configuredto deliver pacing pulses having pulse widths or durations of greaterthan or equal to fifteen (15) milliseconds. In yet another example, ICD14 may be configured to deliver pacing pulses having pulse widths ordurations of greater than or equal to twenty (20) milliseconds.Depending on the pulse widths, ICD 14 may be configured to deliverpacing pulses having pulse amplitudes less than or equal to twenty (20)volts, deliver pacing pulses having pulse amplitudes less than or equalto ten (10) volts, deliver pacing pulses having pulse amplitudes lessthan or equal to five (5) volts, deliver pacing pulses having pulseamplitudes less than or equal to two and one-half (2.5) volts, deliverpacing pulses having pulse amplitudes less than or equal to one (1)volt. Typically the lower amplitudes require longer pacing widths asillustrated in the experimental results. Reducing the amplitude ofpacing pulses delivered by ICD 14 reduces the likelihood of extracardiacstimulation.

ICD 14 may sense electrical activity of heart 26 via a combination ofsensing vectors that include combinations of electrodes 32 and 34 andthe housing or can electrode of ICD 14. For example, ICD 14 may obtainelectrical signals sensed using a sensing vector between electrodes 32and 34, obtain electrical signals sensed using a sensing vector betweenelectrode 32 and the conductive housing or can electrode of ICD 14,obtain electrical signals sensed using a sensing vector betweenelectrode 34 and the conductive housing or can electrode of ICD 14, or acombination thereof. In some instances, ICD 14 may sense electricalactivity of heart 26 via a sensing vector between one of electrode 32(or electrode 34) and electrodes 24, 28 and 30 of lead 16. ICD 14 maydeliver the pacing therapy as a function of the electrical signalssensed via one or more of the sensing vectors of lead 18. Alternativelyor additionally, ICD 14 may deliver the pacing therapy as a function ofthe electrical signals sensed via the one or more of the sensing vectorsof lead 16.

ICD 14 also analyzes the sensed electrical signals from one or more ofthe sensing vectors of lead 18 and/or one or more of the sensing vectorsof lead 16 to detect tachycardia, such as ventricular tachycardia orventricular fibrillation. In some instances, ICD 14 delivers one or moreATP therapies via the one or more pacing or therapy vectors of lead 18in response to detecting the tachycardia in an attempt to terminate thetachycardia without delivering a defibrillation shock. If the one ormore ATP therapies are not successful or it is determined that ATPtherapy is not desired, ICD 14 may deliver one or more defibrillationshocks via defibrillation electrode 24 of lead 16.

The configuration described above in FIGS. 1A-1C is directed toproviding ventricular pacing via lead 18. In situations in which atrialpacing is desired in addition to or instead of ventricular pacing, lead18 may be positioned further superior. A pacing lead configured todeliver pacing pulses to both the atrium and ventricle may have moreelectrodes. For example, the pacing lead may have one or more electrodeslocated over a cardiac silhouette of the atrium as observed viafluoroscopy and one or more electrodes located over a cardiac silhouetteof the ventricle as observed via fluoroscopy. A pacing lead configuredto deliver pacing pulses to only the atrium may, for example, have oneor more electrodes located over a cardiac silhouette of the atrium asobserved via fluoroscopy. In some instances, two substernal pacing leadsmay be utilized with one being an atrial pacing lead implanted such thatthe electrodes are located over a cardiac silhouette of the atrium asobserved via fluoroscopy and the other being a ventricle pacing leadbeing implanted such that the electrodes are located over a cardiacsilhouette of the ventricle as observed via fluoroscopy

ICD 14 may include a housing that forms a hermetic seal that protectscomponents of ICD 14. The housing of ICD 14 may be formed of aconductive material, such as titanium. ICD 14 may also include aconnector assembly (also referred to as a connector block or header)that includes electrical feedthroughs through which electricalconnections are made between conductors within leads 16 and 18 andelectronic components included within the housing. As will be describedin further detail herein, housing may house one or more processors,memories, transmitters, receivers, sensors, sensing circuitry, therapycircuitry and other appropriate components. Housing 34 is configured tobe implanted in a patient, such as patient 12.

Leads 16 and 18 include a lead body that includes one or more electrodeslocated near the distal lead end or elsewhere along the length of thelead body. The lead bodies of leads 16 and 18 also contain one or moreelongated electrical conductors (not illustrated) that extend throughthe lead body from the connector assembly of ICD 14 provided at aproximal lead end to one or more electrodes of leads 16 and 18. The leadbodies of leads 16 and 18 may be formed from a non-conductive material,including silicone, polyurethane, fluoropolymers, mixtures thereof, andother appropriate materials, and shaped to form one or more lumenswithin which the one or more conductors extend. However, the techniquesare not limited to such constructions.

The one or more elongated electrical conductors contained within thelead bodies of leads 16 and 18 may be coupled to one or more ofelectrodes 24, 28, 30, 32, and 34. In one example, each of electrodes24, 28, 30, 32, and 34 is electrically coupled to a respective conductorwithin its associated lead body. The respective conductors mayelectrically couple to circuitry, such as a therapy module or a sensingmodule, of ICD 14 via connections in connector assembly, includingassociated feedthroughs. The electrical conductors transmit therapy froma therapy module within ICD 14 to one or more of electrodes 24, 28, 30,32, and 34 and transmit sensed electrical signals from one or more ofelectrodes 24, 28, 30, 32, and 34 to the sensing module within ICD 14.

The examples illustrated in FIGS. 1A-C are exemplary in nature andshould not be considered limiting of the techniques described in thisdisclosure. In other examples, ICD 14, lead 16, and lead 18 may beimplanted at other locations. For example, ICD 14 may be implanted in asubcutaneous pocket in the right chest. In this example, lead 16 may beextend subcutaneously from the device toward the manubrium of thesternum and bend or turn and extend subcutaneously inferiorly from themanubrium of the sternum, substantially parallel with the sternum andlead 18 may extend subcutaneously from the device toward the manubriumof the sternum to the desired location and bend or turn and extendsubsternally inferiorly from the manubrium of the sternum to the desiredlocation.

In the example illustrated in FIGS. 1A-C, system 10 is an ICD systemthat provides pacing therapy. However, these techniques may beapplicable to other cardiac systems, including cardiac resynchronizationtherapy defibrillator (CRT-D) systems, cardioverter systems, orcombinations thereof.

In addition, it should be noted that system 10 may not be limited totreatment of a human patient. In alternative examples, system 10 may beimplemented in non-human patients, e.g., primates, canines, equines,pigs, bovines, ovines, and felines. These other animals may undergoclinical or research therapies that may benefit from the subject matterof this disclosure.

FIGS. 2, 3A and 3B illustrate an embodiment of a delivery system 100 forimplanting a medical electrical lead in a substernal space of a patient.The delivery system 100 may be utilized to create a pathway through thebody of patient 12 to access an implant location within the substernalspace. The delivery system 100 will be discussed in conjunction withFIGS. 2, 3A, and 3B, where FIG. 2 depicts a perspective view, FIG. 3Adepicts a side cross-sectional view, and FIG. 3B shows a transversesectional view.

The delivery system 100 includes a sheath 102, an elongate tool 104 anda handle 106. The sheath 102 includes a continuous lumen through whichthe elongate tool 104 is disposed. The continuous lumen may extendbetween openings at a proximal end and a distal end of the sheath 102such that, in use, the sheath 102 is slidingly-disposed over theelongate tool 104 during axial advancement of the elongate tool 104through patient 12 to facilitate an implant procedure.

In some embodiments, the sheath 102 may include a slit segment 118 thatis formed proximate to the proximal end. The slit segment 118 may extendpartially through or entirely along a length of the wall of sheath 102.For example, the slit segment 118 may be formed as perforations thatextend from the inner to outer surface along the side wall of sheath102. The slit segment 118 facilitates the slitting of the sheath 102during the implant procedure. In use, the lead 18 will be advanced tothe target site via the lumen of sheath 102. After placement of the lead18, the sheath 102 may be separated from the lead so as to withdraw thesheath 102 from the patient 12 by slitting the side walls of the sheath102 at the slit segment 118.

The inventors of the present disclosure have discovered that it may bedesirable to implant the lead 18 such that it overlies the cardiacsilhouette of the heart 26 as visualized through an imaging techniquefor effective therapy delivery by the lead 18. Yet, it may be desirablenot to place the lead 18 in direct contact with the heart tissue.Therefore, the present disclosure addresses techniques for implantingthe lead 18 in the substernal space underneath the sternum.

Accordingly, one embodiment of the elongate tool 104 includes apre-biased curvature 108 that is formed along a length of the body ofelongate tool 104 proximate to a distal end 110 of the elongate tool. Asshown in FIG. 2, the pre-biased curvature 108 is configured such thatthe segment of the elongate body 104 adjacent to the distal end 110 iscurved to orient the distal portion in a non-parallel plane relative tothe plane defined by the proximal portion. The angle of curvature of thepre-biased curvature is predicated on orienting the section of theelongate tool 104 that is proximal to distal end 110 at an angle that issubstantially perpendicular to the sternum of patient 12 while the restof the elongate tool 104 is generally parallel to the sternum of patient12. For example, the pre-biased curvature 108 is configured having abend that orients the distal end 110 at an angle that is greater than 5degrees relative to a first plane, with the first plane being definedalong a central axis of the proximal portion of the elongate tool 104.

The distal end 110 is configured to provide a tactile signal in responseto contact with tissue, bone or other anatomical features along apathway from the access point into the substernal space of patient 12 toa desired implant location. For example, the pre-biased curvature 108may be oriented such that the distal end 110 is placed in contact withthe sternum, or more particularly the sternebrae. Continuing with theexample, the distal end 110 contacts the various bones along the ribcageor at the fusion point between the ribs and the sternum or with thesternum itself as the elongate tool 104 is advanced during theimplantation. Responsive to the contact between the elongate tool 104and the patient 12, distal end 110 creates a tactile signal thatprovides an indication of the position of the distal end 110 relative tothe patient 12.

An additional benefit of the pre-biased curvature 108 is that itpositions the distal end 110 away from the body cavity and the organsunderneath the sternum by orienting the distal end 110 towards thesternum during navigation of the elongate tool with the substernalspace.

Sheath 102 may be formed from a pliable material such as bio-compatibleplastic including polyaryletheretherketone (PEEK) thermoplastic,PARYLENE® polyxylylene polymers, or other suitable polymer material. Theelongate tool 104 may be formed from a rigid material such as a metalincluding, titanium or stainless steel. In other embodiments, theelongate tool 104 material is a bio-compatible rigid material such, forexample, as TECOTHANE® thermoplastic polyurethanes that may have elastic“memory” properties.

The handle 106 facilitates maneuvering of the elongate tool 104. Assuch, the handle 106 is coupled to the proximal end 112 of the elongatetool 104. The handle 106 may be formed from materials that are similarto those of the elongate tool 104 or from a dissimilar material. Handle106 further includes a directional indicator 116 that provides anindication of the orientation of the pre-biased curvature 108 of thedistal end 110. As will be discussed below, the handle 106 mayalternatively be formed in a predefined shape, such that the shape ofthe handle will provide an indication of the orientation of thepre-biased curvature 108.

The directional indicator 116 provides a visual indicator of theorientation of distal end 110 positioned within the body of patient 12from the exterior of the patient 12. In addition, the directionalindicator 116 will facilitate re-orientation of the distal end 110during navigation of the delivery system 100 within the body of patient12, such, for example, as the navigation to the substernal space.

The delivery system 100 may deliver a fluid through a port or an openingto tissue adjacent to the port or opening. As will be discussed below inconjunction with embodiments of FIGS. 4, 5 and 6, the fluid may be heldin a reservoir of the delivery system 100, or delivered from an externalreservoir through the delivery system 100.

In one embodiment, elongate tool 104 may be provided with a lumen(s) anda fluid dispersion port(s) (not shown) for passage of the fluids throughthe lumen to be dispensed through the opening or port along the lengthof the elongate tool 104. Such a lumen is configured to dispense thefluid through an opening at the distal end 110. The lumen may facilitatedelivery of a fluid such as a therapeutic solution, such as antibioticsor antimicrobial agents, or any other fluid solution (e.g., a contrastsolution) during an implantation procedure of a medical electrical leadinto the substernal space. For example, the fluid may be a medicalanesthetic substance that is delivered into the tissue adjacent to theimplant pathway as the elongate tool 104 is advanced through thepatient. Alternatively, or in addition, the fluid may be a contrastsolution that facilitates visualization of the elongate tool 104 toverify the location of the distal end 110.

In some embodiments, a radiopaque marker element 114 may be disposed onthe elongate tool 104 and/or sheath 102. In the illustrative embodimentof FIG. 2, for instance, the element 114 is depicted overlaying asegment of the distal end 110. Nevertheless, it should be understoodthat the element 114 may overlay or coat any other section or sectionsof the elongate tool 104 or may alternatively overlay the entireelongate tool 104. Element 114 may be formed from a band of radiopaquematerial that is coupled to the distal end 110 through any suitablemechanism. In other embodiments, the distal-most portion of the elongatetool 104 may be formed from a radiopaque material. The radiopaquematerial may include a compound, such as barium sulphate, that isvisible through a fluoroscopic imaging procedure. In use, the markerelement 114 can provide a visual depiction or image of the distal end110.

In other embodiments, one or more mapping electrodes 130 may bepositioned on the sheath 102 or the elongate tool 104. The mappingelectrodes 130 may be used in conjunction with, or as a substitute forthe radiopaque marker element 114 to facilitate mapping of the locationof the delivery system 100 within the substernal implant location. Themapping electrodes 130 are electrically coupled to a location mappingunit such as that disclosed in U.S. Pat. No. 7,850,610 issued toFerek-Petric, which is incorporated herein by reference in its entirety.

In one embodiment, the elongate tool 104 and sheath 102 may be sizedsuch that the dimensions of the lumen of sheath 102 will permitinsertion of elongate tool 104 and/or the lead 18 therethrough. In anexample, sheath 102 may suitably be formed having a lumen having adiameter in the range of 4 French (Fr) to 12 Fr, and preferably a 10.5Fr diameter and having a length ranging from between 6 inches and 24inches, it being understood that the length may further be customizedoutside those dimensions to cater for the variation of the human anatomyfrom patient-to-patient. It should be appreciated that the length of theelongate tool 104 is dimensioned to be slightly longer, for example 2inches longer, than the sheath 102. This relative difference will ensurethat the distal-most portion of the tool 104, including distal end 110,is exposed distally of the distal opening of the sheath 102. Forillustrative purposes, it should be appreciated that the length of theelongate tool 104 is dimensioned having a length that enables the distalend 110 of the elongate tool 104 to be positioned adjacent to the firstrib within the substernal space and extend to an incision performed onthe skin adjacent to the xiphoid process of patient 12, with theproximal end 112 being located external to the patient 12.

FIGS. 4-6 depict alternative embodiments of delivery systems forimplanting a medical electrical lead in a substernal space of a patient.FIGS. 7, 8, 9 and 10, 11, and 12 illustrate cross sectional views ofalternative embodiments of an elongate tool. In particular, FIG. 7depicts a side cross-sectional view of any one of the elongate bodiesdepicted in FIGS. 4-6, and FIG. 10 shows the corresponding transversesectional view. FIG. 8 depicts a side cross-sectional view of any one ofthe elongate bodies depicted in FIGS. 4-6, and FIG. 11 shows thecorresponding transverse sectional view. FIG. 9 depicts a sidecross-sectional view of any one of the elongate bodies depicted in FIGS.4-6, and FIG. 12 shows the corresponding transverse sectional view.

Each of the delivery systems 200 a-c (collectively, “delivery system(s)200”) includes an elongate tool 204 and a handle 206 a-d (collectively,“handle(s) 206”). A distal portion of the elongate tool 204 of thedelivery systems 200 includes a pre-biased curvature that may correspondto the pre-biased curvature 108 described in conjunction with FIG. 2. Afluid insertion port 222 is provided on any of the handles 206 a-d thatmay be in fluid communication with one or more fluid lumen(s) 224disposed within the elongate tool 204. One or more fluid dispersionports or openings (not shown) are provided in fluid communication withthe fluid lumens 224 for delivery of the fluid.

The handle 206 a is formed with a directional indicator 220 a that isintegrally formed with the handle and that can be visualized on theexternal surface. The handle 206 a is configured to provide anindication of the orientation of the distal end of elongate tool 204.The directional indicator 220 a may comprise a projection formed on aportion of the handle 206 a that is shaped as a prominently visibleprotrusion. The directional indicator 220 a such as a detent, that isdirected towards a plane that is parallel to the plane of the curvedportion of the distal end of the elongate tool 204.

The handle 206 b illustrated in FIG. 5 includes a reservoir (not shown)that may be configured to hold a fluid for delivery through the lumen224 of elongate tool 204. A plunger 226 may be provided to control theinjection of fluid through the lumen 224.

The handle 206C illustrated in the alternative embodiment of FIG. 6 iscoupled to an external reservoir that holds a fluid that is deliveredthrough the elongate tool 204.

FIG. 13 depicts another embodiment of a delivery system 250 forimplanting a medical electrical lead in a substernal space of a patient.The delivery system 250 includes a sheath 252, an elongate tool 254, ahandle 256, and a sealing assembly 258. System 250 will be discussed inconjunction with FIGS. 14, 15A, and 15B, where FIG. 14 depicts a partialside cross-sectional view of the sheath 252 and sealing assembly 258,and FIGS. 15A and 15B show transverse sectional views of the sealingassembly 258.

Sheath 252 may be constructed with the distal terminal end having atapered profile. Providing the tapered distal end reduces the traumacaused to patient 12 during advancement of the system 250 in an implantprocedure. The sheath 252 includes a continuous lumen 260 through whichthe elongate tool 254 is disposed. The lumen 260 (shown in dashed lines)may extend distally from a proximal opening to a distal end 262 tofacilitate axial advancement of the elongate tool 254 therethroughduring an implant procedure.

A slit segment 264 a may be provided along the wall of sheath 252 toenable slitting of the sheath 252 during the implant procedure. The slitsegment 264 a may be provided at the proximal end of the sheath 252.

In accordance with an embodiment, the elongate tool 254 is constructedwith a pre-biased curvature 266 that extends proximally from the distalend 262. The pre-biased curvature 266 forms a bend at a locationsituated about 1 to 4 inches from the distal end 262. The angle ofcurvature of the pre-biased curvature may vary from between 1 degree to20 degrees relative to an imaginary axial line formed by the proximalportion of the elongate tool, so as to orient the distal end 262 towardsa different plane relative to the axial plane defined by the proximalportion of the elongate tool 254.

In use, the distal end 262 may provide a tactile signal as described inconjunction with the distal end 110 responsive to contact with tissue,bone or other anatomical features along a pathway from the access pointinto the substernal space of patient 12 to a desired implant location.The pre-biased curvature 266 also positions the distal end 262 away fromthe body cavity and the organs underneath the sternum by orienting thedistal end 262 towards the sternum during navigation of the elongatetool 254 with the substernal space.

Sheath 252 may be formed from a pliable material such as bio-compatibleplastic including polyaryletheretherketone (PEEK) thermoplastic,PARYLENE® polyxylylene polymers, a polyether block amide such as Pebax®,a polyolefin such as Pro-fax, or other suitable polymer material. Thedistal end 262 of sheath 252 may be constructed from an elastomer suchas polyether block amide, or polyamide 12 and/or with a hydrophiliccoating or any other material that facilitates gliding of the distal endover the elongate tool 254. The elongate tool 254 may be formed from arigid material such as a metal including, titanium or stainless steel.In other embodiments, the material for elongate tool 254 is abio-compatible rigid material such, for example, as TECOTHANE®thermoplastic polyurethanes that may have elastic “memory” properties.

The handle 256 is coupled to the proximal end 274 of the elongate tool254. The handle 256 facilitates maneuvering of the elongate tool 254.Embodiments of the handle 256 may resemble the handles 106, or 206. Thehandle 256 is depicted having a directional indicator 268 thatfacilitates visualization of the orientation of distal end 262. Inaddition, the directional indicator 268 will facilitate re-orientationof the distal end 262 during navigation of the delivery system 250within the body of patient 12, such, for example, as the navigation tothe substernal space.

The delivery system 250 may further include a fluid lumen for deliveryof a fluid through a port or an opening to tissue adjacent to the portor opening as discussed in conjunction with embodiments of FIGS. 7-12.

In other embodiments, a radiopaque marker element 270 may be disposed onthe elongate tool 254. In the illustrative embodiment of FIG. 13, forinstance, the element 270 is depicted overlaying two segments of thedistal portion. Element 254 may be formed as a band of radiopaquematerial that is coupled to the elongate tool through coating or anyother any suitable mechanism. The material of the radiopaque markerelement 270 may include a compound, such as barium sulphate, that isvisible through a fluoroscopic imaging procedure. In use, the markerelement 270 can provide a visual depiction or image of the distalportion of elongate tool 254 within the patient 12. In otherembodiments, the marker element 270 may be coupled to the sheath 252instead of or in addition to being coupled to the elongate tool 254.

As described above, the elongate tool 254 and the sheath 252 may besized such that the dimensions of the sheath 252 will permit insertionof a lead 18 therethrough.

It may be desirable to prevent air from being pushed into the bodycavity of the patient 12 during the implant procedure of the lead 18.Preventing the introduction of air within the body cavity facilitatesthe effectiveness of therapy delivery to the patient. This may furtherassist in establishing the threshold parameters for the patient 12during the implant procedure.

Accordingly, the sheath 252 is provided with the sealing assembly 258that prevents or reduces the amount of air that is pushed into the bodycavity during the implant procedure. Thus, the sealing assembly 258 maybe disposed proximal to a proximal opening into the lumen 260 to providea seal into the lumen 260 of sheath 252. The sealing assembly 258defines a passage 272 therethrough that is substantially aligned withthe lumen 260. As used herein, substantially aligned refers to thecentral axis of the lumen 260 and the central axis of the passage 272being adjacent to each other such that the lumen 260 and passage 272 arein fluid communication. In addition, substantially aligned refers to thealignment of the passage 272 with a portion of the lumen 260 especiallybecause of the dimensional differences as will be discussed below.

As shown in the illustrations of FIGS. 15A and 15B, the sealing assembly258 is configured such that passage 272 defines a first diameter D1prior to introduction of an accessory device such as the elongate tool254 or lead 18, and a second diameter D2 responsive to insertion of theaccessory device. Hence, the diameter D1 is less than the diameter D2.In an embodiment, the sealing assembly 258 tapers distally towards theintersection of the passage 272 with the lumen 260. For example, thepassage 272 may expand up to 100% of the diameter of the lumen 260 or aslittle as 0.1% of the diameter of the lumen 260. The sealing assembly258 is constructed such that the diameter D1 is tailored to accommodatepassage of the accessory devices, e.g., elongate tool 254 and the lead18, while providing an interference seal to prevent ingress of airaround the outer circumference of the accessory device. In order toaccommodate variations in the diameters of the accessory devices, thesealing assembly 258 is formed from materials that have the necessaryelongation properties to prevent permanent deformation during insertionand passage of the accessory devices. Such a material may include arelatively soft and resilient material, for example, a liquid siliconerubber (LSR) material or a thermoplastic elastomer (TPE) material, ascompared to the material that forms the sheath 252.

The sealing assembly 258 may also be formed having a slit segment 264 bthat extends from an exterior surface of the sidewall to the interiorsurface. The slit segment 264 b is formed such that it is continuouswith the slit segment 264 a to create a continuous slit path. As hasbeen described above, the slit segment 264 b in conjunction with slitsegment 264 a will enable the sheath 252 to be separate from the lead 18during an implant procedure.

Although the sealing assembly 258 is depicted being positioned proximateto the proximal end 274, it should be understood that the sealingassembly 258 may suitably be positioned anywhere along a length of thesheath 252.

FIG. 16 is a flow chart 300 of a method of implanting a lead accordingto an embodiment of the present invention. FIGS. 17-19 are partialperspective views that illustrate the method 300 of implanting the lead18 at a suitable implant location within a substernal space 6. FIGS.18-19 depict a schematic view of the ribcage 4 of patient 12. Thesternum 22 is a flat, narrow bone comprising three segments: themanubrium, the body, and the xiphoid process.

At task 302, an incision 2 is made on the skin/tissue adjacent to orbelow the xiphoid process (also referred to as “subxiphoid”) to form anaccess point sized for passage of a delivery system and/or a lead (FIG.17) to the substernal space. The access point may also be formed at thenotch (not shown) that connects the xiphoid process to the sternum. Inother embodiments, the substernal space may also be accessed through themanubrium. FIG. 17 illustrates the exemplary anterior or pectoralincision 2 on patient 12. The incision location provides access to thesubsternal space 6 underneath the ribcage 4 and is sized to allowinsertion of a delivery system for navigation of the lead. The leade.g., lead 18, may be coupled to an implantable medical device 14 thatis implantable or implanted in a subcutaneous location. As such aportion of the lead 18 may be tunneled through subcutaneous tissue fromthe device 14 to the incision location.

A delivery system 1000 is provided for facilitating the lead implant(304). The delivery system 1000 may be embodied as any of theaforementioned delivery systems 100, 200, 250, or combinations thereof,described in conjunction with FIGS. 2-15B that include a sheath, anelongate tool, a catheter and optionally a sealing assembly. Thedelivery system 1000 will be provided with the elongate tool beingdisposed within the lumen of the sheath.

At task 306, delivery system 1000 is inserted through the incision. Asdescribed above, the exemplary delivery systems include an elongatedbody having a pre-biased curvature at the distal end. At task 308, thecurved distal portion is oriented such that the distal end is pointedtowards the sternum (FIG. 18). A directional indicator on the handle ofthe delivery system may be utilized to assist in placement or to confirmthe proper orientation of the distal end. The directional indicator mayresemble any one of those described in conjunction with the precedingfigures.

At task 310, the elongated body of the delivery system is advancedwithin the substernal space underneath the sternum in a generally axialdirection from the xiphoid process towards the jugular notch. During theadvancing of the delivery system, the distal end is navigated in directcontact or close proximity with the sternum. In some embodiments, afluid may be delivered during the advancing of the delivery system intothe substernal space at task 312. For example, the delivery system maydeliver an analgesic agent or a contrast solution or any other suitablefluid. Optionally, a signal is generated that is indicative of thelocation of the distal end of the delivery system (314). The signal maybe a tactile signal such as a sensation or sound that is generated inresponse to the interaction of the distal end with various segments ofthe sternum or ribs of the ribcage connected to the sternum.Alternatively, or in addition, an imaging procedure may be performed toobtain an image of a segment of the delivery system. To that end, theradiopaque marker elements described above may be utilized inconjunction with fluoroscopy during the advancing of the delivery system1000 to obtain a visual indication of the directional orientation of thedistal portion of the delivery system within the patient. With the aidof the signal(s), the delivery system is navigated such that a distalportion is positioned at a target implant location of the distal end ofthe lead (FIG. 19).

Upon confirmation that the delivery system has been positioned at theappropriate location, the elongate tool is then removed from the sheath(316). Subsequent to withdrawing the elongate tool from the lumen of thesheath, the lead is then advanced through the body along the length ofthe lumen of the sheath (318).

It is during this exchange of the elongate tool with the lead body thatpotential air can be trapped in the tubing and pushed into the bodycavity of the patient in the substernal space 6. As such, a deliverysystem such as that disclosed in FIGS. 14-15B may be utilized inaccordance with some embodiments of the method. The sealing mechanism ofsuch a delivery system will seal the distal opening of the sheath toprevent air from filling the lumen. When such a catheter is used,advancing of the lead into the sheath will not push air (or will pushonly a minimal amount of air) into the substernal space 6.

At task 320, the lead is advanced to the implant location through thedelivery system. In one embodiment, the elongated body of the deliverysystem may be retracted from the sheath, leaving the sheath positionedwithin the substernal space. In other embodiments, the delivery systemmay have a lumen for insertion of the lead through the lumen. The leadmay be preloaded within the lumen of the delivery system, in someexamples, prior to insertion of the delivery system into the substernalspace. At task 322, the lead is positioned at the appropriate implantlocation. In some embodiments, the positioning may include orienting theelectrodes to provide a targeted stimulation therapy and/or fixation ofthe lead to the tissue at the implant site.

At task 324, the sheath is withdrawn from the patient 12 and the leadremains within the substernal space. In accordance with someembodiments, a slittable sheath such as those described above may beutilized. Slitting of the sheath may be performed in accordance withconventional techniques, for example, utilizing a slitting tool. Theslittable sheath facilitates withdrawal of the sheath by separating thebody of the sheath from the lead to ensure that the lead placement isnot impacted as the sheath is pulled distally away from the incision 2.At task 326, the lead may be coupled to a stimulation pulse generator,such as ICD 14. In other embodiments the lead may be tunneled from theaccess point to the ICD 14 that is positioned subcutaneously on the leftmidaxillary of patient 12.

As described herein, delivery systems in accordance with variousembodiments are provided that facilitate implantation of a lead in thesubsternal space. In alternative implementations, the delivery systemsmay be utilized for delivery of a lead in locations other than thesubsternal space including but not limited to the aforementionedextra-pericardial space.

Various examples have been described. It is contemplated that thefeatures described in the different embodiments may be combined tocreate additional embodiments. All such disclosed and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method of delivering an implantable medicalsystem, comprising: providing a delivery system comprising a sheathhaving a lumen and a sealing assembly having a passage that is in fluidcommunication with the lumen, and an elongate tool disposed within thelumen and the passage; creating an access point into a substernal spaceof a patient; inserting the delivery system through the access pointinto the substernal space; orienting a distal portion of the deliverysystem towards a sternum of the patient; advancing the delivery systemthrough the substernal space to a predetermined implant site; generatingwith the distal portion a signal indicative of a location of the distalportion relative to the sternum during the task of advancing; removingthe elongate tool from the lumen and the passage and inserting a leadthrough the passage into the lumen; advancing the lead of theimplantable medical system to position a distal end of the lead at thepredetermined location; and positioning an electrode coupled to thedistal end of the lead in a predetermined orientation within thesubsternal space.
 2. The method of delivering the implantable medicalsystem of claim 1, wherein the elongate tool is formed having a distalterminal end and a distal portion that is curved to orient the distalterminal end of the elongate tool towards the sternum.
 3. The method ofdelivering the implantable medical system of claim 1, further comprisingobtaining an indication of a location of the distal portion of thedelivery system relative to the substernal space during the task ofadvancing the delivery system.
 4. The method of delivering theimplantable medical system of claim 3, wherein obtaining the indicationcomprises obtaining a fluoro image of a section of the delivery system.5. The method of delivering the implantable medical system of claim 1,further comprising delivering a fluid to the substernal space throughthe delivery system during the advancing of the delivery system.
 6. Themethod of delivering the implantable medical system of claim 5, whereinthe delivered fluid is one of a fluoro-visible media, a therapeuticfluid, and an analgesic agent.
 7. The method of delivering theimplantable medical system of claim 5, wherein the delivery systemcomprises an elongate tool having a fluid lumen for delivery of thefluid.
 8. The method of delivering the implantable medical system ofclaim 1, further comprising obtaining an indication of the orientationof the distal portion of the delivery system relative to the substernalspace.
 9. The method of delivering the implantable medical system ofclaim 1, further comprising retracting the elongate tool from the sheathand utilizing the lumen to advance the lead.
 10. The method ofdelivering the implantable medical system of claim 1, wherein accessingthe substernal space comprises performing an incision at a locationadjacent to a xiphoid process of the patient.
 11. The method ofdelivering the implantable medical system of claim 8, wherein the stepof generating a signal indicative of a location of the distal portion ofthe medical system relative to the sternum comprises generating a signalindicative of a location of a distal portion of the elongated tool. 12.The method of delivering the implantable medical system of claim 1,wherein the step of generating a signal indicative of a location of thedistal portion of the medical system relative to the sternum comprisesgenerating a signal indicative of a location of a distal portion of theelongated tool.
 13. A method of delivering an implantable medicalsystem, comprising: providing a delivery system comprising a sheathhaving a lumen and a sealing assembly having a passage that is in fluidcommunication with the lumen, and an elongate tool disposed within thelumen and the passage; creating an access point into a substernal spaceof a patient; inserting the delivery system through the access pointinto the substernal space; orienting a distal portion of the deliverysystem towards a sternum of the patient; advancing the delivery systemthrough the substernal space to a predetermined implant site; generatingwith the distal portion a signal indicative of a location of the distalportion relative to the sternum during the task of advancing; removingthe elongate tool from the lumen and the passage and inserting a leadthrough the passage into the lumen; advancing the lead of theimplantable medical system to position a distal end of the lead at thepredetermined location; and positioning an electrode coupled to thedistal end of the lead in a predetermined orientation within thesubsternal space; and wherein generating the signal comprises navigatingthe distal portion of the delivery system to be in contact with asternum of the patient and receiving a tactile signal indicative of arelative position of the distal portion of the delivery system withrespect to the sternum.
 14. The method of delivering the implantablemedical system of claim 13, wherein the distal portion of the deliverysystem includes a pre-biased curvature oriented to form a bend of thedistal portion of the delivery system.
 15. The method of delivering theimplantable medical system of claim 13, wherein the step of generating asignal indicative of a location of the distal portion of the medicalsystem relative to the sternum comprises generating a signal indicativeof a location of a distal portion of the elongated tool.